Plunger pump tappet assembly and roller thereof

Abstract

A plunger pump includes a plunger pump tappet assembly and a roller. The roller includes a revolving body configured to revolve along a central axis. The revolving body includes logarithmic parts and a straight part which are integrally formed. The logarithmic parts are symmetrically provided at two ends of the straight part in an axial direction of the central axis. In a cross section of the revolving body along and through the central axis, an outline of the straight part forms a straight line, and an outline of the logarithmic part forms a logarithmic curve, with an X-axis lying along the central axis, and a perpendicular bisector of the X-axis as a Y-axis.

What is claimed is: 
     
       1. A roller for a tappet assembly of a plunger pump, comprising:
 a revolving body configured to revolve along a central axis, the revolving body having logarithmic parts and a straight part integrally formed with the logarithmic parts, 
 wherein the logarithmic parts are symmetrically located at two ends of the straight part in an axial direction of the central axis, 
 wherein a cross section of the revolving body, along and through the central axis, defines an outline including (i) an outline portion of the straight part that forms a straight line, and (ii) another outline portion of the straight part and each logarithmic part that form logarithmic curves, 
 wherein an upper edge along the outline defines an X-axis, and 
 wherein a line perpendicular to the X-axis and passing through an axial center of the roller defines a Y-axis, 
 wherein the logarithmic curves conform to the following function: 
 
       
         
           
             
               { 
               
                 
                   
                     
                       
                         y 
                         = 
                         
                           0 
                           ⁢ 
                           
                             ( 
                             
                               x 
                               ≤ 
                               5 
                             
                             ) 
                           
                         
                       
                     
                   
                   
                     
                       
                         y 
                         = 
                         
                           
                             
                               - 
                               0.008 
                             
                             · 
                             ln 
                           
                           ⁢ 
                           
                             7 
                             
                               7 
                               - 
                               
                                 2.3 
                                 · 
                                 
                                   
                                     [ 
                                     
                                       
                                         2 
                                         ⁢ 
                                         
                                           ( 
                                           
                                             x 
                                             - 
                                             5 
                                           
                                           ) 
                                         
                                       
                                       7 
                                     
                                     ] 
                                   
                                   2 
                                 
                               
                             
                           
                         
                       
                     
                   
                 
                 ⁢ 
                 
                     
                 
                 ⁢ 
                 
                   
                     ( 
                     
                       5 
                       < 
                       x 
                       ≤ 
                       10.4 
                     
                     ) 
                   
                   . 
                 
               
             
           
         
       
     
     
       2. The roller according to  claim 1 , wherein the revolving body defines a central hole. 
     
     
       3. The roller according to  claim 1 , wherein the straight part accounts for 40-50% of an axial length of the revolving body along the central axis. 
     
     
       4. A tappet assembly, comprising:
 a tappet defining a receiving slot; and 
 a roller disposed in the receiving slot, the roller including a revolving body configured to revolve along a central axis, the revolving body having logarithmic parts and a straight part integrally formed with the logarithmic parts, 
 wherein the logarithmic parts are symmetrically located at two ends of the straight part in an axial direction of the central axis, 
 wherein a cross section of the revolving body, along and through the central axis, defines an outline including (i) an outline portion of the straight part that forms a straight line, and (ii) another outline portion of the straight part and the logarithmic part that forms a logarithmic, 
 wherein an upper edge along the outline defines an X-axis, and 
 wherein a line perpendicular to the X-axis and passing through an axial center of the roller defines a Y-axis. 
 
     
     
       5. The tappet assembly according to  claim 4 , wherein:
 the roller defines a central hole, and 
 a pin is located in the central hole.